Rail guided brush assemblies are known, see for example, EP1592112. Rail brush assemblies comprise a pair of rails and a brush having two grooves on opposite sides thereof. The brush slides along the rails towards the commutator of the motor urged by a spring and captured by the rails being located within the grooves.
One problem with this arrangement is that at end of life, the brushes can dislodge from the rails and cause a short circuit within the motor which could lead to catastrophic failure.